In a medium pot, combine chopped rhubarb, sugar, and water and heat over medium heat for 10-12 minutes, or until the rhubarb is completely broken down. Transfer mixture to a blender and puree until smooth. Set aside.
Preheat oven to 350°F. Line a 9×13 baking dish with parchment paper and set aside.
In a standing mixer fitted with a whisk attachment, cream the butter, cream cheese, sugar, salt and vanilla extract until light and fluffy, about 2 minutes. Turn mixer to low speed and incorporate flour.
Press dough firmly onto the bottom of the baking dish, spreading evenly to the edges. Bake for 15 minutes.
While the shortbread is cooking, make the rhubarb curd! In a large bowl, whisk all ingredients except for the flour. Use as much red dye as you’d like, and remember that the color will fade a bit during cooking. Once mixed, whisk in the flour.
Pour the rhubarb curd on top of the cream cheese shortbread, then bake for an additional 20 minutes to set the rhubarb.
Cool bars for at least 4 hours in fridge, then cut and top with powdered sugar!